Add isPowerOfTwo functions.

src/algorithms/math/is-power-of-two/isPowerOfTwoBitwise.js

@@ -0,0 +1,31 @@
+/**
+ * @param {number} number
+ * @return {boolean}
+ */
+export default function isPowerOfTwoBitwise(number) {
+  // Don't work with negative numbers.
+  if (number < 0) {
+    throw new Error('Please provide positive number');
+  }
+
+  // 0 and 1 are not powers of two.
+  if (number <= 1) {
+    return false;
+  }
+
+  /*
+   * Powers of two in binary look like this:
+   * 1: 0001
+   * 2: 0010
+   * 4: 0100
+   * 8: 1000
+   *
+   * Note that there is always exactly 1 bit set. The only exception is with a signed integer.
+   * e.g. An 8-bit signed integer with a value of -128 looks like:
+   * 10000000
+   *
+   * So after checking that the number is greater than zero, we can use a clever little bit
+   * hack to test that one and only one bit is set.
+   */
+  return (number & (number - 1)) === 0;
+}